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Ecology Lecture 15: Patterns of Life Histories and Seed Dispersal Strategies in Plants - P, Study notes of Ecology and Environment

A portion of a university ecology lecture focused on patterns of life histories in animals and plants, seed size and number in plants, and life history variation among and within species. The lecture covers concepts such as semelparity and iteroparity, seed dispersal strategies, and r and k selection. It also includes examples and research findings.

Typology: Study notes

Pre 2010

Uploaded on 08/18/2009

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Ecology (BIOL 250)
Lecture 15:
Patterns of Life Histories
AnnouncementsToday’s Outline
Offspring Numb er Versus
Size
Animals
Plants
Life History Vari ation Among
Species
Life History Clas sification
R - Selected
K - Selected
New Models
Sexual selection
Offspring Number Versus Size
!Principle of Allocation: If organisms use
energy for one function such as growth,
the amount of energy available for
other functions is reduced.
"Leads to trade-offs between functions such
as number and size of offspring.
!Semelparity
"Initially, invest all energy in growth and storage.
"Followed by one massive suicidal act of
reproduction (examples?)
! Iteroparity
"Produce fewer offspring at a time.
"Repeat reproduction throughout their lifetime.
(examples?)
Offspring Number Versus Size
Seed Size and Number in Plants
!Many families produce small number of
larger seeds. . . But some produce a
great number of tiny seeds.
"Dispersal mode influences seed size.
!What are some examples of dispersal modes?
!Why might they influence seed size
Seed Size and Number in Plants
!Westoby et.al. recognized six seed
dispersal strategies:
"Unassisted: No specialized structures.
"Adhesion: Hooks, spines, or barbs.
"Wind: Wings, hair, (resistance structures).
"Ant: Oil surface coating (elaisome).
"Vertebrate: Fleshy coating (aril).
"Scatterhoarded: Gathered,stored in caches.
Seed Size and Number in Plants
!Jakobsson and Eriksson (2000) found
seed size variation explained many
differences in recruitment success.
"Larger seeds produce larger seedlings and
were associated with increased recruitment
(seed production).
pf3

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Ecology (BIOL 250 ) Lecture 15 : Patterns of Life Histories Today’s Outline Announcements Offspring Number Versus Size Animals Plants Life History Variation Among Species Life History Classification R - Selected K - Selected New Models Sexual selection Offspring Number Versus Size !Principle of Allocation: If organisms use energy for one function such as growth, the amount of energy available for other functions is reduced. "Leads to trade-offs between functions such as number and size of offspring. !Semelparity "Initially, invest all energy in growth and storage. "Followed by one massive suicidal act of reproduction (examples?) ! Iteroparity "Produce fewer offspring at a time. "Repeat reproduction throughout their lifetime. (examples?) Offspring Number Versus Size Seed Size and Number in Plants !Many families produce small number of larger seeds... But some produce a great number of tiny seeds. "Dispersal mode influences seed size. !What are some examples of dispersal modes? !Why might they influence seed size Seed Size and Number in Plants ! Westoby et.al. recognized six seed dispersal strategies: "Unassisted: No specialized structures. "Adhesion: Hooks, spines, or barbs. "Wind: Wings, hair, (resistance structures). "Ant: Oil surface coating (elaisome). "Vertebrate: Fleshy coating (aril). "Scatterhoarded: Gathered,stored in caches. Seed Size and Number in Plants ! Jakobsson and Eriksson ( 2000 ) found seed size variation explained many differences in recruitment success. "Larger seeds produce larger seedlings and were associated with increased recruitment (seed production).

Seed Size and Number in Plants ! Small plants producing large numbers of small seeds appear to have an advantage in areas of high disturbance. " WHY ?!#%!!? ! Plants producing large seeds are constrained to producing fewer seedlings. " Should these seedlings be more or less capable of surviving environmental hazards than their small seeded counterparts?

Life History Variation among Species

! Shine and Charnov pointed out vertebrate energy budgets are different before and after sexual maturity. "Before - maintenance or growth. "After - maintenance, growth, or reproduction. "Individuals delaying reproduction will grow faster and reach a larger size. !Increased reproduction rate. ! Gunderson found clear relationship between adult fish mortality and age of reproductive maturity. "Species with higher mortality show higher relative reproductive rate.

Life History Variation among Species

! Bertschy and Fox studied the influence of adult survival on pumpkinseed sunfish life histories. "Findings supported theory that when adult survival is lower relative to juvenile survival, natural selection will favor allocating greater resources to reproduction.

Life History Variation within Species

Life History Classification ! MacArthur and Wilson ( 1967 ) "r selection (per capita rate of increase) !Characteristic high population growth rate. "K selection (carrying capacity) !Characteristic efficient resource use. ! Pianka ( 1972 ) "r and K are ends of a continuum, while most organisms are in-between. !r selection: Unpredictable environments. !K selection: Predictable environments. r and K Selection: Fundamental Contrasts !Intrinsic Rate of Increase: "Highest in r selected species. !Competitive Ability: "Highest in K selected species. !Reproduction: "r: Numerous individuals rapidly produced. "K: Fewer larger individuals slowly produced. r (^) K